I recently read an article that claimed that snakes once had full arms and legs until something causedthem to genetically mutate about 150 million years ago. There are two new studies that address themutation of snake DNA, specifically ZRS, or Zone of Polarizing Activity Regulatory Sequence. This is theDNA that is responsible for limb-altering change. The first study is titled, Progressive Loss of Function ina Limb Enhancer during Snake Evolution, published in the Journal Cell. The second is Loss and Re-emergence of Legs in Snakes by Modular Evolution of Sonic hedgehog and HOXD Enhancers, in CurrentBiology.

It is interesting that the two studies used different approaches to prove the same thing. The first studyused mice. They took mice embryos and removed their ZRS DNA and replaced it with the ZRS sectionfrom snakes. This interchange was devastating for the mice. The mice barely grew any limbs at all. Thisproves that the ZRS element is absolutely necessary for the development of limbs.The second study differentiated two sorts of snakes. Snakes closer to the base of the snake family tree,meaning that they were closer to ancient snakes, still have vestigial legs, or tiny bones buried within theirmuscles. These snakes are represented by boas and pythons. More advanced snakes, such as the viper andcobra, have no physical traces of limb structures. In this study, research focused on a gene called hedgehogwhich is essential in embryonic development. Hedgehog is also a key in limb formation. What theresearchers discovered was that that the sonic hedgehog regulators in snakes had mutated. The researchersvalidated their claims by applying a DNA editing technique called CRISPR to extract the ZRS stretch inmice embryos and replace it with the ZRS from other animals, including that of snakes. When the micehad ZRS DNA from other animals, including fish and humans, they developed limbs, just as any normalmice would. But, when researchers replaced it with ZRS from pythons and cobra, the limbs of mice failedto form. In further examination of the snakes’ ZRS, researchers discovered that there is a deletion ofseventeen base pairs. They performed another experiment in which they meticulously repaired the 17 basepairs of snakes and inserted these into mice embryos. Astonishingly, the mice grew legs.Both studies showed that the ZRS of the DNA chain is responsible for limb development. The ZRScomponent contains the DNA instruction for making limbs in humans and other legged vertebrates. This isinteresting because it is not that snakes lack the ZRS component. Rather, it is clear that their ZRS has beenaltered through evolution. That the ZRS component of differing species can be interchanged and befunctional is absolutely astonishing for me because it supports an important concept expressly taught in theLotus Sutra.

That snakes and people had once shared limbs supports the concept of equality as is found in Chaptertwo of the Lotus Sutra. As much as we may abhor snakes, we cannot deny the above data that snakes andhumans both have the ZRS gene. The second chapter of the Lotus Sutra, Hoben-pon, in essence, claims thesame thing. Hypothetically, when we disperse our bodies and minds into small bits and pieces, and analyzethem, we should be able to find components that are similar between people who we think are differentbecause they are of a different sex, height, weight, skin color, or demeanor. The Buddha encourages us tosee deep within people to find their commonality, thus invalidating any minor differences that we may haveon the surface.